The present invention relates to an apparatus and method for performing spine surgery, and more particularly, to a working channel for minimally invasive spine surgery and a method for using the working channel.
Referring to prior art FIGS. 1A and 1B, the spine 120, also known as the vertebral column or the spinal column, is a flexible column of vertebrae 100 (special types of bones) held together by muscles, ligaments and tendons. The spine 120 extends from the cranium (not shown) to the coccyx 126, encasing a spinal cord 128 and forming the supporting axis of the body (not shown). The spinal cord 128 is a thick bundle of nerve tissue (nerves) that branch off to various areas of the body for the purposes of motor control, sensation, or the like. The spine 120 includes seven cervical vertebrae (not shown), twelve thoracic vertebrae (not shown), five lumbar vertebrae, L1-LV, five sacral vertebrae, S1-SV, and three coccyx vertebrae 126. The sacral and coccyx vertebrae are each fused, thereby functioning as a single unit. FIG. 1B shows the lumbar region 122, the sacral region 124 and the coccyx 126 of the spine 120 and that the vertebrae 100 are stacked one upon another. The top portion 100a and bottom portion 100b of each vertebrae 100 is slightly concave. The opposing concave vertebral surfaces form the intervertebral space 121 in which an intervertebral disk (not shown) resides. Each of the intervertebral disks has a soft core referred to as a nucleus pulposus or nucleus (not shown).
In FIG. 1A, directional arrow 101a is pointing in the posterior direction and directional arrow 101b is pointing in the anterior direction. FIG. 1A shows that each vertebrae 100 includes a body 106 in the innermost portion, a spinal canal 108 and a spinous process 102 at the posterior-most end of the vertebra 100. The vertebrae 100 are substantially similar in composition, but vary in size from the larger lumbar to the smallest coccyx vertebrae 126. Each vertebrae 100 further includes two transverse processes 104 located on either side and a protective plate-like structure referred to as a lamina 110. Nerves from the spinal cord 128 pass through the spinal canal 108 and foramina 111 to reach their respective destinations within the body.
Recently, less invasive surgical techniques referred to as “minimally invasive” surgery have been developed to reduce the surgical trauma to a patient during spine surgery. In minimally invasive surgery, a much smaller incision is made than in normal open surgeries. A small retractor, working channel or tube is inserted through the posterior muscles (not shown) to allow access to the spine. Surgeons utilize special surgical instruments modified to work in such small openings such as curettes, osteotomes, reamers, probes, retractors, forceps or the like to access the spine while monitoring their technique using a microscope, fluoroscope (real-time X-ray monitoring), and/or an endoscope (a miniature TV camera with associated viewing monitor).
In order to access the area of interest in a minimally invasive spinal surgery, a working tube is installed through an incision in a patient's back. Presently available working tubes are typically round or ovoid. The round or ovoid shape places pressure on the skin in the area around an incision because the incisions are typically linear. Additionally, the round shape restricts access with surgical instruments between spinous processes and between pedicle and facet structures, thereby restricting possible movement of the instruments. Even further, the round shape makes moving the working tube along the sagittal plane difficult because of the large amount of surface area that is being pressed against muscle.
It is desirable to provide a working channel for minimally invasive spine surgery and a method for using such a working channel in order to allow access by a surgical instrument for performing minimally invasive spinal surgeries. The working channel should be easy to use, safe to insert into the body during surgery, provide for improved access and should not cause undesired damage to adjacent vertebrae. It is desirable to provide a minimally invasive surgical technique that allows for fast patient recovery times and that can be used on an outpatient basis.